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Stromatolites

Stromatolites. whole mounds. Shark Bay Western Australia. section view. “Living fossil” stromatolite reefs (made by cyanobacteria) of Shark Bay Australia. Paleozoic stromatolite fossils (ARP). www-cyanosite.bio.purdue.edu/images/images.html. Voyaging & Ocean Exploration.

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Stromatolites

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  1. Stromatolites whole mounds Shark Bay Western Australia section view “Living fossil” stromatolite reefs (made by cyanobacteria) of Shark Bay Australia Paleozoic stromatolite fossils (ARP) www-cyanosite.bio.purdue.edu/images/images.html

  2. Voyaging & Ocean Exploration

  3. Early Voyaging: Pacific Islanders & Polynesians Text pg. 14 A bamboo “stick chart” of the Marshall Islands shows islands (shells at junctions), regular ocean wave direction (straight strips), and waves that bend around islands (curved strips). Similar stick charts were used by early Polynesians Text pg. 13 Pacific islanders (“Lapita people”) were present in New Ireland 5000 – 4000 BC and reached Fiji, Tonga, and Samoa by ~1100 BC. By ~500 AD they had reached Hawaii and begun regular trade across 3,500 km of open ocean!

  4. Early Voyaging: Mediterranean & Mapping Herodotus (450 BC) Eratosthenes (~200 BC) Text pg. 9 • Greeks & Phoenecians trade widely in Mediterranean by 1200 BC; extensive records kept at the great library in Alexandria (Egypt) founded by Alexander the Great in 307 BC • Herodotus (~450 BC)- map with no ref. lines • Eratosthenes* (~200 BC)- reference lines tied to geographical features • Hipparchus* (~145 BC)- regular latitude & longitude lines (degrees; no copies known) • Ptolemy* (~150 AD)- divided degrees of latitude & longitude into minutes & seconds • Library in Alexandria burned (415 AD) Ptolemy (150 AD) Text pg. 17 * librarians or scholars at Alexandria

  5. Eratosthenes estimated earth’s circumference ~200BC Three observations: 1) sunlight reached the bottom of a vertical well at Syene at noon on the longest day of the year 2) a vertical flagpole in Alexandria cast a shadow of 7.2 degrees 3) the distance between these sites was 800 km Two assumptions: 1) earth was a sphere 2) sun was very far away so that rays of sunlight were parallel Text pg. 16 Eratosthenes (2nd chief librarian in Alexandria) computed the earth’s circumference to within 8%!

  6. Early Voyaging: Vikings Some notable events: • 62 ships raid Morocco in 859 AD • colonize Iceland by 860 AD • colonize Newfoundland by 985 AD Text pg. 18

  7. Early Voyaging: Europeans Text pg. 19 Some notable events: • Columbus reaches New World in 1492 • Ferdinand Magellan (actually his boat) is first to circumnavigate the globe (1519-1522) • Cook’s three voyages around the world (1768, 1772, 1776) Text pg. 20

  8. The problem of Longitude Finding latitude is easy, finding longitude is hard • Most early navigators would “run the latitude” • Determining longitude became a high priority to the British navy in early 1700’s • In 1707, 2000 British sailors died on return from a successful battle with the French • After two weeks of travel in the fog the admiral’s navigator said land was still far off • One sailor objected. His own records showed they should be nearing shore. He was hung for insubordination! • In 1714 Parliament offered a 20,000 pound prize to find longitude to ± 0.5 degree (50 km) • John Harrison (a clockmaker) made a chronometer that passed this test in 1759 but was denied the prize by the astronomers who ran the “British Board of Longitude” until 1773 Text pg. 8 John Harrison’s first chronometer David Sobel’s book on the story

  9. Important marine science voyages • Cook’s voyages (1768, 1772, 1776) were first to include many biological and scientific studies • Darwin’s voyage on the Beagle (1831-36) revolutionized thinking about coral reefs and evolution • Challenger Expedition (1872-76) defines “Birth of Oceanography” • Prompted by a great debate over whether life existed in the deep sea • Research on ocean chemistry benthic & plankton biology was published in 50 volumes; a total of 4,717 new species were described • Probably greatest oceanographic expedition of all time Text pg. 23 Text pg. 22

  10. The Scientific Method The “Scientific Method” is much misunderstood • What is its most valuable contribution? - does it yield more or better ‘facts’? - is it a better source of new hypotheses? - does it yield longer-lasting hypotheses? • It provides a set of rules whereby two people who disagree about ‘causes & effects’ can agree on a test to decide who is right; it is really a dispute-resolution method: observation, hypothesis, test • Two common misconceptions are: - ‘tests’ require experiments (in reality, crucial observations also provide tests) - ‘hypotheses’ are proven (in reality, they are simply not yet rejected; the choice is always between alternative hypotheses) • It “Makes the mystical discussable” (E. E. Ruppert) Text pg. 6 The text’s summary of the scientific method

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